Note: Descriptions are shown in the official language in which they were submitted.
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A SOAP BAR WITH HIGH WATER CONTENT
Field of the invention
The present invention relates to a soap bar composition. It particularly
relates to fatty
acid soap bars made by a rapid extrusion process. It more particularly relates
to a soap
bar composition that comprises high amount of water from about 20 to 40% water
and
yet is easy to extrude and stamp. It also ensures maintaining good quality bar
properties.
Background of the invention
Surfactants have been used for personal wash applications for a long time.
There are
many categories of products in the personal wash market e.g. body wash, face
wash,
hand wash, soap bars, shampoos, etc. Products which are marketed as body wash,
face wash and shampoos are generally in liquid form and are made of synthetic
anionic
surfactants. They are generally sold in plastic bottles/ containers. Soap bars
and hand
wash products generally contain soaps. Soap bars do not need to be sold in
plastic
containers and are able to retain their own shape by virtue of being
structured in the form
of a rigid solid. Soaps bars are usually sold in cartons made of cardboard.
Soap bars are generally prepared through one of two routes. One is called the
cast bar
route while the other is called the milled and plodded route (also known as
extrusion
route). The cast bar route has inherently been very amenable in preparing low
TFM
(total fatty matter) bars. TFM is defined as the total amount of fatty matter,
mostly fatty
acids, that can be separated from a sample of soap after splitting with a
mineral acid,
usually hydrochloric acid. In the cast bar soaps, the soap mixture is mixed
with polyhydric
alcohols and poured in casts and allowed to cool and then the soap bars are
removed
from the casts. The cast bar route enables production at relatively lower
throughput rates.
In the milled and plodded route, the soap is prepared with high water content
and then
spray dried to reduce the moisture content and to cool the soap after which
other
ingredients are added and then the soap is extruded through a plodder and
optionally
cut and stamped to prepare the final soap bar. The milled and plodded soaps
generally
have a high TFM in the range of 60 to 80 weight percent.
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Milled and plodded soap bars are also known as extruded soap bars. They are
composed of very many different types of soaps. Most soap compositions
comprise both
water insoluble as well as water soluble soaps. Their structure is generally
characterized
by a brick and mortar type structure. Insoluble soaps (called bricks) usually
consist of
higher chain C16 and C18 soaps (palmitate and stearate soap). They are
generally
included in soap bars to provide structuring benefits i.e. they provide shape
to the bars.
Soap bars also consist of water soluble soaps (which act as the mortar) which
are
generally unsaturated C18:1 and 18:2 sodium soap (oleate soap) in combination
with
short chain fatty acids (generally C8 to C12 or even up to C14 soap). Water
soluble
soaps generally aid in cleaning.
In addition to about the 60 ¨ 80 wt% TFM, soap bars presently prepared through
the
extruded route for personal wash contain about 14-22 wt% water. There is a
need for
developing sustainable technologies where one approach is to develop soaps
with lower
TFM content and by increasing the water content with no compromise on the
cleaning
efficacy. The present inventors are aware of various attempts by the present
applicants
and others to reduce the fatty matter content. These technologies include
approaches to
structure soap bars, like inclusion of natural aluminosilicate clays like
bentonite or
kaolinite but they are found to not be very efficient in structuring the bars
at low amounts.
If one simply substitutes the TFM with higher amount of water, it causes
problems during
extrusion of the soap mass and further the extruded bars are sticky and cannot
be
stamped easily.
To counter the effect of increased water levels, it is also possible to add
electrolytes to
soap. The electrolyte serves to "shorten" the soap by which is meant that the
soap bar
increases in hardness and becomes less sticky. However, the addition of
electrolytes
provides its own set of negative attributes; for example, it leads to greater
degree of
cracking or fissures in the extruded bars (to a level unacceptable by
consumer); and
further can lead to formation of an electrolyte layer on the bar surface which
is visible to
the naked eye, a phenomenon referred to as "efflorescence".
It is thus extremely difficult to provide predominantly fatty acid soap
surfactant based
bars which have high levels of water, which can be extruded at speed of 200
bars per
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minute and higher; and which do not simultaneously suffer from the problem of
undesirable cracking and/or efflorescence (electrolyte formation) during bar
storage.
Unexpectedly, applicants have now found that, through use of a specific
polymer
especially in the presence of controlled amounts of the specific electrolytes,
it is possible
to provide high extrusion, high water bars while avoiding the problems of bar
cracking
and bar efflorescence, particularly when storing. Soap bars with inclusion of
polymers
e.g. acrylate polymers are known e.g. US5703026 (P&G, 1997) discloses a skin
cleansing bar soap composition comprising (a) from about 40 to about 95%
surfactant
component comprising fatty acid soap and/or synthetic surfactant, such that
the
composition comprises: (i) from 0 to 95% fatty acid soap; and (ii) from 0% to
about 50%
synthetic surfactant; (b) particles of absorbent gellant material, dry weight
basis, in the
composition being from about 0.02% to about 5%, the absorbent gellant material
having
an extractable polymer content of less than about 25%; and (c) from about 5 to
about
35% water and additionally other optional ingredients.
WO 2019/025257 discloses a soap bar comprising soap, at least one perfume oil,
at
least one polymer, optionally water, and optionally further known cosmetic
ingredients
other than the soap, the perfume oil, the polymer and the water, wherein the
at least one
polymer is a water-soluble polymer, wherein the polymer has a water solubility
of at least
0.01 g of polymer in 100 g of water at 20 C at one or more than one pH value
in the
range between (4) and (9), and wherein the at least one polymer is selected
from the
group consisting of a polymer in which more than 20 wt% of the repeating units
of the
polymer are repeating units derived from at least one ethylenically
unsaturated,
polymerizable monomer having at least one acid group, and a polymer comprising
repeating units derived from N-vinylpyrrolidone, wherein the proportion of
these
repeating units in the polymer is at least 50 wt%.
The present inventors have found that inclusion of commonly available acrylate
polymers
does not provide as good a structuring property to soap bars as compared to
the specific
polymer claimed in the present invention.
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It is thus an object of the present invention to provide for a low TFM soap
bar which can
be prepared using the extrusion route and is easily and conveniently
stampable.
It is another object of the present invention to provide for a low TFM soap
bar which in
addition to being conveniently extrudable and stampable does not compromise on
the
bar integrity or sensorial properties.
Summary of the invention
The present invention relates to a soap bar composition comprising
(i) 20 to 75 wt% anhydrous soap;
(ii) a polymer comprising
(a) 39 to 59% by weight of the polymer, structural units of C1-4 alkyl
acrylate;
(b) 40 to 60% by weight of the polymer, structural units of (meth)acrylic
acid;
(c) 1 to 10% by weight of the polymer, structural units of a specialised
associative monomer having formula 1
0
R liOCH2CH2)-0
R2 =(I)
Wherein R1 is a linear C10-28 alkyl group, preferably C18-26,
Wherein each R2 is independently a hydrogen or a methyl group; and
Wherein n has a value in the range of 20 to 28; and
(iii) 20 to 40 wt% water.
Detailed description of the invention
These and other aspects, features and advantages will become apparent to those
of
ordinary skill in the art from a reading of the following detailed description
and the
appended claims. For the avoidance of doubt, any feature of one aspect of the
present
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invention may be utilized in any other aspect of the invention. The word
"comprising" is
intended to mean "including" but not necessarily "consisting of" or "composed
of." In
other words, the listed steps or options need not be exhaustive. It is noted
that the
examples given in the description below are intended to clarify the invention
and are not
5 intended to limit the invention to those examples per se. Similarly, all
percentages are
weight/weight percentages unless otherwise indicated. Except in the operating
and
comparative examples, or where otherwise explicitly indicated, all numbers in
this
description and claims indicating amounts of material or conditions of
reaction, physical
properties of materials and/or use are to be understood as modified by the
word "about".
Numerical ranges expressed in the format "from x to y" are understood to
include x and
y. When for a specific feature multiple preferred ranges are described in the
format "from
x to y", it is understood that all ranges combining the different endpoints
are also
contemplated.
The present invention relates to a soap bar composition. By a soap bar
composition is
meant a cleansing composition comprising soap which is in the form of a shaped
solid.
The soap bar of the invention is useful for cleaning any surface e.g. those
used for
cleaning clothes (e.g. laundering) or for personal cleansing. It is especially
useful for
personal cleansing. The soap bar of the present invention comprises 20 to 75%
soap,
preferably 40 to 75%, more preferably 40 to 60wt% soap by weight of the soap
bar
composition. The term soap means salt of fatty acid. Preferably, the soap is
soap of C8
to C24 fatty acids. Preferably, the soap bar composition of the present is an
extruded
soap bar.
The cation may be an alkali metal, alkaline earth metal or ammonium ion,
preferably
alkali metals. Preferably, the cation is selected from sodium or potassium,
more
preferably sodium. The soap may be saturated or unsaturated. Saturated soaps
are
preferred over unsaturated soaps for stability. The oil or fatty acids may be
of vegetable
or animal origin.
The soap may be obtained by saponification of oils, fats or fatty acids. The
fats or oils
generally used to make soap bars may be selected from tallow, tallow stearins,
palm oil,
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palm stearins, soya bean oil, fish oil, castor oil, rice bran oil, sunflower
oil, coconut oil,
babassu oil, and palm kernel oil. The fatty acids may be from coconut, rice
bran,
groundnut, tallow, palm, palm kernel, cotton seed or soyabean.
The fatty acid soaps may also be synthetically prepared (e.g. by the oxidation
of
petroleum or by the hydrogenation of carbon monoxide by the Fischer-Tropsch
process).
Resin acids, such as those present in tall oil, may also be used. Naphthenic
acids may
also be used.
The soap bar may additionally comprise synthetic surfactants selected from one
or more
from the class of anionic, non-ionic, cationic or zwitterionic surfactants,
preferably from
anionic surfactants. These synthetic surfactants, as per the present
invention, are
included in less than 8%, preferably less than 4%, more preferably less than
1% and
sometimes absent from the composition.
The composition of the present invention is in the form of a shaped solid for
example a
bar. The cleaning soap composition is a wash off product that generally has a
sufficient
amount of surfactants included therein that it is used for cleansing the
desired surface
like topical surface e.g. the whole body, the hair and scalp or the face. It
is applied on
the topical surface and left thereon only for a few seconds or minutes and
washed off
thereafter with copious amounts of water. Alternately it may be used for
laundering
clothes. The soap bar is usually rubbed on to the wet clothes, optionally
brushed and
then rinsed with water to remove the residual soap and dirt.
The soap bars of the present invention preferably includes low molecular
weight soaps
(C8 to C14 soaps) which are generally water soluble, which are in the range of
2 to 20%
by weight of the composition. It is preferred that the soap bar includes 15 to
55 wt% of
the soap of 016 to 024 fatty acid, which are generally water insoluble soaps.
Unsaturated fatty acid soaps preferably at 15 to 35% may also be included in
the total
soap content of the composition. Unsaturated soaps are preferably oleic acid
soaps.
In an especially preferred aspect, the soap bar comprises 20 to 75%,
preferably 25 or 30
or 31 or 32 or 35 or 40% on lower level to 70% or 65% by wt. on upper level
anhydrous
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soap. The C16 to C24 saturated soap in such bar composition comprises 12 to
45% by
wt. of total bar.
Preferably short chain C8 to C14 fatty acid soaps are included at 2 to 20% by
wt. of total
bar. Also preferably unsaturated C18 fatty acid having, one, two or three
unsaturated
groups in the C18 chain comprises 6% to 35%, more preferably 12 to 35% by wt.
of total
bar.
It is also possible to replace a part of the soaps with solvent (e.g.
glycerine) without
compromising on cleansing. This can also reduce the costs of the bar and could
also
bring additional benefits for consumers, such as mildness. In such bars, it is
preferred
that the ratio of [soap] to [water plus any water-soluble solvent] which may
be present
(polyol such as glycerine or sorbitol) is in a ratio of 0.5:1 to 5:1,
preferably 1:1 to 3:1.
Since it is typically preferred to have less soap and more water, ratios on
the lower end
(1:1 t02:1) are particularly preferred.
The novel structurant in bars of the present invention is a polymer
comprising:
(a) 39 to 59% by weight of the polymer (preferably 44 to 58%,
more preferably 47 to
55%, most preferably 48 to 52%) structural units of C1-4 alkyl acrylate;
(b) 40 to 60% by weight of the polymer (preferably 40.5 to 55%, more
preferably 41
to 50%, most preferably 41.5 to 45%) structural units of (meth)acrylic acid;
(c) 1 to 10% by weight of the polymer (preferably 2.5 to 7.5%,
more preferably 3 to
7%, most preferably 3.5 to 6% structural units of a specialised associative
monomer having formula 1
0
R ¨(-0CH2CH2)-0y
R2 0)
Wherein R1 is a linear C10-28 alkyl group, preferably C18-26, more preferably
C20-24,
most preferably C21-23;
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Wherein each R2 is independently a hydrogen or a methyl group, preferably at
least 80
mol% of the R2 groups are a methyl group; more preferably wherein at least 95
mol%
of the R2 groups are a methyl group; further more preferably wherein at least
99 mol%
of the R2 groups are a methyl group; and
Wherein n has a value in the range of 20 to 28 (preferably 22 to 26; more
preferably 23
to 27; most preferably 24 to 26).
By n having a value in the range of 20 to 28 is meant that the average value
of n is to lie
in this range. It is possible that the associative monomer of formula 1 above
is prepared
by a process where the chain length of the (OCH2CH2) group varies in a certain
range
but the average value of the chain lengths is a value in the range of 20 to
28.
The most preferred polymer for structuring the bars of the invention comprises
(a) 49.7 to 51.8% by weight of the polymer of structural units of ethyl
acrylate;
(b) 41.5 to 43.3 wt% structural units of (meth)acrylic acid, wherein 95 to 100
wt% of the
structural units of (meth)acrylic acid are structural units of methacrylic
acid; and
(c) 4.5 to 4.7 wt% structural units of a specialised associative monomer
having the
formula 1
0
R +C H 2CH2)--0
R2 ()
Wherein R1 is a linear 022 alkyl group;
Wherein each R2 is a hydrogen or a methyl group, wherein 80 to 100 mol% of the
R2
groups are methyl groups; and
Wherein n has a value in the range of 24 to 26.
The polymer is preferably included in 0.01 to 5% more preferably 0.05 to 3 %,
and most
preferably 0.1 to 2 % by weight of the soap bar composition.
While the polymer of the present invention structures water in soap, it is
preferred that
the composition includes electrolytes. While electrolytes are known to harden
bars, they
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typically result in extruded bars which are so hard and brittle they have
excessive
cracking and/or provide efflorescence (layer of electrolyte) on the bar
surface, particularly
on storage.
The present inventors have found that the polymer as disclosed herein is
especially
useful if the bar includes specific types and amounts of electrolytes. With
the electrolyte
system described below, bars can be extruded and stamped at high rate while
avoiding
excessive cracking and efflorescence. The bars have defined minimal hardness
and low
stickiness scores.
Electrolytes as per this invention include compounds that substantially
dissociate into
ions in water. Electrolytes as per this invention are not ionic surfactants.
Suitable
electrolytes for inclusion in the soap making process are alkali metal salts.
Preferred
alkali metal salts for inclusion in the composition of the invention include
sodium sulfate,
sodium chloride, sodium acetate, sodium citrate, potassium chloride, potassium
sulfate,
sodium carbonate and other mono or di or tri salts of alkaline earth metals,
more
preferred electrolytes are sodium chloride, sodium sulfate, sodium citrate,
potassium
chloride and especially preferred electrolyte is sodium chloride, sodium
citrate or sodium
sulphate or a combination thereof. For the avoidance of doubt, it is clarified
that the
electrolyte is a non-soap material. It is especially preferred that the soap
bar composition
of the invention includes an electrolyte system as defined below.
The electrolyte system is a specific combination of alkali metal chloride (in
defined
amounts) together with secondary electrolyte which can be alkali metal
citrate, alkali
metal sulfate, or mixtures of the citrate and sulfate, wherein the secondary
electrolyte(s)
is also used in specific defined amounts whether alone or as a mixture. The
alkali metal
may be sodium or potassium preferably sodium.
The amount of electrolyte providing this benefit is defined as follows:
1. [alkali metal chloride] % = 0.075 x [water] ¨ 0.626; and
2. [alkali metal citrate] % = - 0.0023 x [water]2 +0.312x[water] ¨4.34;
[alkali metal sulfate] % = - 0.0023 x [water]2 +0.312x[water] ¨ 4.34; or
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[alkali metal citrate plus alkali metal sulfate] % = - 0.0023 x [water]2
+0.312x[water] ¨ 4.34,
wherein the calculated amount of the concentration of the electrolyte is plus
or minus
5 15% (e.g., if calculated concentration of sodium chloride is 0.86 based
on the formula, it
may be based at level of 0.86 0.129% by wt. The calculated amount of the
concentration of the electrolyte is preferably plus or minus 10%, furthermore
preferably
plus or minus 5%.
10 Based on the above formula, developed with extensive experimentation by
the inventors,
the preferred amounts of electrolytes for various preferred range of water is
summarised
below:
Water from 20 to 40 wt% of the bar:
Sodium chloride could be included in the range of 0.74 to 2.73%, preferably
0.79 to
2.61%, most preferably 0.83 to 2.49% by weight of the bar.
Sodium sulphate or sodium citrate or a combination of the two could be
included in
0.83 to 5.13%, preferably 0.88 to 4.91%, most preferably 0.93 to 4.68% by
weight of
the bar.
Water from 20 to 35 wt% of the bar:
Sodium chloride could be included in the range of 0.74 to 2.30%, preferably
0.79 to
2.20%, most preferably 0.83 to 2.10% by weight of the bar.
Sodium sulphate or sodium citrate or a combination of the two could be
included in
0.83 to 4.33%, preferably 0.88 to 4.14%, most preferably 0.93 to 3.95% by
weight of
the bar.
Water from 25 to 35 wt% of the bar:
Sodium chloride could be included in the range of 1.06 to 2.30%, preferably
1.12 to
2.20%, most preferably 1.19 to 2.10% by weight of the bar.
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Sodium sulphate or sodium citrate or a combination of the two could be
included in
1.72 to 4.33%, preferably 1.82 to 4.14%, most preferably 1.92 to 3.95% by
weight of
the bar.
The soap bar composition of the invention preferably comprises an electrolyte.
In total, the electrolyte is preferably included in 0.1 to 8%, more preferably
0.5 to 6%,
even more preferably 0.5 to 5%, furthermore preferably 0.5 to 3%, and most
preferably
1 to 3% by weight of the composition. It is preferred that the electrolyte is
included in the
soap bar during the step of saponification to form the soap.
The high levels of water used in the bars of the invention are in the range of
20% to 40%,
preferably 25% to 40%, preferably 26% or 27% or 28% or 29% or 30% by wt. as
lower
limit and 39 or 38 or 37 or 36 or 35% as upper limit, where any lower limit
can be used
interchangeably with any upper limit. If such high amount of water were used
in bars
previously known in the art, it typically results in bars which are soft and
tacky (compared
to bars of our invention which are defined by a certain minimum hardness and
low
stickiness score). Such bars, previously known in the art, have difficulty
extruding and
stamping at a high extrusion rate of 200 bars per minute and greater.
Using such defined components (Soap, polymer, electrolyte amounts; ratio of
soap to
water and optional solvent), we can obtain bars which are extruded at 200 or
more
bars/minute and have hardness value of 1.2 Kg to 5.0 Kg (measured at 40 C);
low
stickiness and cracking, and which bars are free of visible efflorescence.
In addition to the long, saturated soaps which act as structurants, bars of
the invention
may optionally comprise 0.05 to 35% structurants. Use of more structurants
permits
lower ratio of [soap] to [water soluble solvent e.g. polyol plus water] if
desired.
The structurant may include one or more structurants such as starches, sodium
carboxymethylcellulose, inorganic particulate matter (e.g., talc, calcium
carbonate,
zeolite and mixtures of such particulates) and mixtures thereof. The combined
level of
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C16 to C24 long chain structurants and structurants noted above is preferably
higher than
25%, preferably, 25% to 40%.
The composition of the invention may comprise selective amount of zeolite
which is in
the range of 3 to 20%, preferably 5 to 15% by weight of the composition.
Zeolites are
hydrated aluminosilicates. Their structure consists in a three dimensional
framework of
interlinked tetrahydra of A104 and SiO4 coordinated by oxygen atoms. Zeolites
are solids
with a relatively open, three-dimensional crystal structure built from the
elements
aluminum, oxygen, and silicon, with alkali or alkaline-earth metals (such as
sodium,
potassium, or magnesium) with water molecules trapped in the gaps between
them.
Zeolites form with many different crystalline structures, which have large
open pores
(sometimes referred to as cavities) in a very regular arrangement and roughly
the same
size as small molecules.
The structural formula of zeolite based on its crystal unit cell (assuming
both the SiO2
and A102 as variables) can be represented by
Main (A102)a (SiO2)b. WH20
Where M is the cation (e.g sodium, potassium or magnesium), w is the number of
water
molecules per unit cell, and a and b are total number of tetrahedra of Al and
Si,
respectively per unit cell; and n is valency of the metal ion. The ratio of
b/a usually varies
from 1 to 5.
E.g. for Mordenite the chemical formula is Nas (A102)8 (S102)40
Where a = 8 and b= 40; b/a is 5.
For Zeolite 4A, the chemical formula is Na96 (A102)96 (SiO2)96
Where a = 96 and b = 96; b/a is 1.
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Some zeolites have b/a value which vary from 10 to 100 or even higher e.g. for
ZSM-5
type of zeolite.
As per this invention zeolites which are preferred for use in the soap
composition include
Zeolite 4A, Zeolite 5A, Zeolite 13A or Zeolite 3A. The most preferred Zeolite
is Zeolite
4A.
The composition of the invention preferably comprises a silicate compound
preferably
sodium silicate or calcium silicate, more preferably sodium silicate.
Sodium
silicate includes compounds having the formula (Na2O)SiO2. The weight ratio of
Na2O
to SiO2 could vary from 1:2 to 1:3.75. Grades of sodium silicate with ratio
from about 1:
2 to 1:2.85 are called alkaline silicate and with ratios from 1:2.85 to about
1:3.75 are
called neutral silicate. Forms of sodium silicate that are available include
sodium
metasilicate (Na2SiO3), sodium pyrosilicate (Na6Si207), and sodium
orthosilicate
(Na4SiO4). It is preferred as per this invention that alkaline sodium silicate
is used.
Especially preferred is alkaline sodium silicate with a ratio of 1:2. It is
preferred that the
soap bar comprises 0.1% to 10 wt% sodium silicate or calcium silicate, on dry
weight
basis.
The soap bar composition may optionally contain some free fatty acids. When
included,
free fatty acids comprise 0.1 to 15%, preferably 0.5 to 12% by weight of free
fatty acids.
By free fatty acids is meant a carboxylic acid comprising a hydrocarbon chain
and a
terminal carboxyl group bonded to an H. Suitable fatty acids are C8 to C22
fatty acids.
Preferred fatty acids are C12 to C18, preferably predominantly saturated,
straight-chain
fatty acids. However, some unsaturated fatty acids can also be employed.
The composition preferably comprises a polyhydric alcohol (also called polyol)
or mixture
of polyols. Polyol is a term used herein to designate a compound having
multiple hydroxyl
groups (at least two, preferably at least three) which is highly water
soluble. Many types
of polyols are available including: relatively low molecular weight short
chain polyhydroxy
compounds such as glycerol and propylene glycol; sugars such as sorbitol,
manitol,
sucrose and glucose; modified carbohydrates such as hydrolyzed starch, dextrin
and
maltodextrin, and polymeric synthetic polyols such as polyalkylene glycols,
for example
polyoxyethylene glycol (PEG) and polyoxypropylene glycol (PPG). Especially
preferred
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polyols are glycerol, sorbitol and their mixtures. Most preferred polyol is
glycerol. In a
preferred embodiment, the bars of the invention comprise 0 to 8%, preferably 1
to 7.5%
by wt. polyol.
The soap composition may be made into a bar by a process that first involves
saponification of the fat charge with alkali followed by mixing with the
polymer and water
and then extruding the mixture in a conventional plodder. The plodded mass may
then
be optionally cut to a desired size and stamped with a desirable indicia. An
especially
important benefit of the present invention is that, notwithstanding the high
amount of
water content of the soap bar, compositions thus prepared by extrusion are
found to be
easy to stamp with a desirable indicia.
By "easy to extrude" is meant that the hardness of the bar as it is extruded
is high enough
that it exits the extruder in a firm enough form that it can be called a rigid
bar. The
hardness of the bar is preferably higher than 1.2 kg, more preferably in the
range of 1.2
to 5.0 kg (at 40 C). The hardness is preferably measured using the TA-XT
Express
apparatus available from Stable Micro Systems. The hardness is measured using
this
apparatus with a 30 conical probe ¨ Part #P/30c to a penetration of 15 mm. If
the soap
mass is too soft and is passed through the extruder it will not extrude out of
the extruder
in a cohesive enough mass to be called a bar. By "easy to stamp" is meant that
the soap
bar is of such a consistency and low enough stickiness that it does not stick
to the die
that is used to stamp any desired indicia on the bar. The soap bar prepared by
the
process of the invention therefore preferably comprises an indicium stamped
thereupon.
The various optional ingredients that make up the final soap bar composition
are as
described below:
Organic and Inorganic Adjuvant Materials
The total level of the adjuvant materials used in the bar composition should
be in an
amount not higher than 50%, preferably 1 to 50%, more preferably 3 to 45% by
wt. of
the soap bar composition.
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Suitable starchy materials which may be used include natural starch (from
corn, wheat,
rice, potato, tapioca and the like), pregelatinized starch, various physically
and
chemically modified starch and mixtures thereof. By the term natural starch is
meant
starch which has not been subjected to chemical or physical modification ¨
also known
5 as raw or native starch. The raw starch can be used directly or modified
during the
process of making the bar composition such that the starch becomes
gelatinized, either
partially or fully gelatinized.
The adjuvant system may optionally include insoluble particles comprising one
or a
combination of materials. By insoluble particles is meant materials that are
present in
10 solid particulate form and suitable for personal washing. Preferably,
there are mineral
(e.g., inorganic) or organic particles.
The insoluble particles should not be perceived as scratchy or granular and
thus should
have a particle size less than 300 microns, more preferably less than 100
microns and
most preferably less than 50 microns.
15 Preferred inorganic particulate material includes talc and calcium
carbonate. Talc is a
magnesium silicate mineral material, with a sheet silicate structure and a
composition of
Mg3Si4(OH)22 and may be available in the hydrated form. It has a plate-like
morphology,
and is essentially oleophilic/hydrophobic, i.e., it is wetted by oil rather
than water.
Calcium carbonate or chalk exists in three crystal forms: calcite, aragonite
and vaterite.
The natural morphology of calcite is rhombohedral or cuboidal, acicular or
dendritic for
aragonite and spheroidal for vaterite.
Examples of other optional insoluble inorganic particulate materials include
aluminates,
silicates, phosphates, insoluble sulfates, and clays (e.g., kaolin, china
clay) and their
combinations.
Organic particulate materials include: insoluble polysaccharides such as
highly
crosslinked or insolubilized starch (e.g., by reaction with a hydrophobe such
as octyl
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succinate) and cellulose; synthetic polymers such as various polymer lattices
and
suspension polymers; insoluble soaps and mixtures thereof.
Bar compositions preferably comprise 0.1 to 25% by wt. of bar composition,
preferably
to 15 by wt. of these mineral or organic particles.
5 An opacifier may be optionally present in the personal care composition.
When opacifiers
are present, the cleansing bar is generally opaque. Examples of pacifiers
include
titanium dioxide, zinc oxide and the like. A particularly preferred opacifier
that can be
employed when an opaque soap composition is desired is ethylene glycol mono-
or di-
stearate, for example in the form of a 20% solution in sodium lauryl ether
sulphate. An
alternative opacifying agent is zinc stearate.
The product can take the form of a water-clear, i.e. transparent soap, in
which case it will
not contain an opacifier.
The pH of preferred soaps bars of the invention is from 8 to 11, more
preferably 9 to 11.
A preferred bar may additionally include up to 30 wt% benefit agents.
Preferred benefit
agents include moisturizers, emollients, sunscreens and anti-ageing compounds.
The
agents may be added at an appropriate step during the process of making the
bars.
Some benefit agents may be introduced as macro domains.
Other optional ingredients like anti-oxidants, perfumes, polymers, chelating
agents,
colourants, deodorants, dyes, enzymes, foam boosters, germicides, anti-
microbials,
lathering agents, pearlescers, skin conditioners, stabilizers or superfatting
agents, may
be added in suitable amounts in the process of the invention. Preferably, the
ingredients
are added after the saponification step. Sodium metabisulphite, ethylene
diamine tetra
acetic acid (EDTA), or ethylene hydroxy diphosphonic acid (EHDP) are
preferably added
to the formulation.
The composition of the invention could be used to deliver antimicrobial
benefits.
Antimicrobial agents that are preferably included to deliver this benefits
include
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oligodynamic metals or compounds thereof. Preferred metals are silver, copper,
zinc,
gold or aluminium. Silver is particularly preferred. In the ionic form it may
exist as a salt
or any compound in any applicable oxidation state. Preferred silver compounds
are
silver oxide, silver nitrate, silver acetate, silver sulfate, silver benzoate,
silver salicylate,
silver carbonate, silver citrate or silver phosphate, with silver oxide,
silver sulfate and
silver citrate being of particular interest in one or more embodiments. In at
least one
preferred embodiment the silver compound is silver oxide. Oligodynamic metal
or a
compound thereof is preferably included in 0.0001 to 2%, preferably 0.001 to
1% by
weight of the composition. Alternately an essential oil antimicrobial active
may be
included in the composition of the invention. Preferred essential oil actives
which may
be included are terpineol, thymol, carvacol, (E) -2(prop-1-enyl) phenol, 2-
propylphenol,
4- pentylphenol, 4-sec-butylphenol, 2-benzyl phenol, eugenol or combinations
thereof.
Furthermore, preferred essential oil actives are terpineol, thymol, carvacrol
or thymol,
most preferred being terpineol or thymol and ideally a combination of the two.
Essential
oil actives are preferably included in 0.001 to 1%, preferably 0.01 to 0.5% by
weight of
the composition.
The invention will now be illustrated by means of the following non-limiting
examples.
Examples
Example A-C and 1-3: Effect of soap bars outside and within the invention on
hardness
of the bars
The following six soap bar compositions as shown in Table ¨ 1 were prepared.
The
hardness of each soap bar was measured using the following procedure:
Hardness Testing Protocol
Principle
A 30 conical probe penetrates into a soap/syndet sample at a specified speed
to a pre-
determined depth. The resistance generated at the specific depth is recorded.
There is
no size or weight requirement of the tested sample except that the bar/billet
be bigger
than the penetration of the cone (15mm) and have enough area. The recorded
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resistance number is also related to the yield stress and the stress can be
calculated as
noted below. The hardness (and/or calculated yield stress) can be measured by
a variety
of different penetrometer methods. In this invention, as noted above, we use
probe
which penetrates to depth of 15 mm.
Apparatus and Equipment
TA-XT Express (Stable Micro Systems)
30 conical probe ¨ Part #P/30c (Stable Micro Systems)
Sampling Technique
This test can be applied to billets from a plodder, finished bars, or small
pieces of
soap/syndet (noodles, pellets, or bits). In the case of billets, pieces of a
suitable size (9
cm) for the TA-XT can be cut out from a larger sample. In the case of pellets
or bits
which are too small to be mounted in the TA-XT, the compression fixture is
used to form
several noodles into a single pastille large enough to be tested.
Procedure
Setting up the TA-XT Express
These settings need to be inserted in the system only once. They are saved and
loaded
whenever the instrument is turned on again. This ensures settings are constant
and that
all experimental results are readily reproducible.
Set test method
Press MENU
Select TEST SETTINGS (Press 1)
Select TEST TPE (Press 1)
Choose option 1 (CYCLE TEST) and press OK
Press MENU
Select TEST SETTINGS (Press 1)
Select PARAMETERS (Press 2)
Select PRE TEST SPEED (Press 1)
Type 2 (mm s-1) and press OK
Select TRIGGER FORCE (Press 2)
Type 5 (g) and Press OK
Select TEST SPEED (Press 3)
Type 1 (mm s-1) and press OK
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Select RETURN SPEED (Press 4)
Type 10 (mm s-1) and press OK
Select DISTANCE (Press 5)
Type 15 (mm) for soap billets or 3 (mm) for soap pastilles and press OK
Select TIME (Press 6)
Type 1 (CYCLE)
Calibration
Screw the probe onto the probe carrier.
Press MENU
Select OPTIONS (Press 3)
Select CALIBRATE FORCE (Press 1) ¨ the instrument asks for the user to check
whether the calibration platform is clear
Press OK to continue and wait until the instrument is ready.
Place the 2kg calibration weight onto the calibration platform and press OK
Wait until the message "calibration completed" is displayed and remove the
weight from
the platform.
Sample Measurements
Place the billet onto the test platform.
Place the probe close to the surface of the billet (without touching it) by
pressing the UP
or DOWN arrows.
Press RUN
Take the readings (g or kg) at the target distance (Fin).
After the run is performed, the probe returns to its original position.
Remove the sample from the platform and record its temperature.
Calculation & Expression of Results
Output
The output from this test is the readout of the TA-XT as "force" (RT) in g or
kg at the
target penetration distance, combined with the sample temperature measurement.
(In
the subject invention, the force is measured in Kg at 40 C at 15 mm distance)
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The force reading can be converted to extensional stress, according to the
equation
below:
The equation to convert the TX-XT readout to extensional stress is
1
a =
CA
5
where: o- = extensional stress
C = "constraint factor" (1.5 for 300 cone)
Gc = acceleration of gravity
74,1 tan
A = projected area of cone =
10 d = penetration depth
0 = cone angle
For a 300 cone at 15 mm penetration Equation 2 becomes
c(Pa) = 128.8
15 This stress is equivalent to the static yield stress as
measured by penetrometer.
The extension rate is
V
dtdA t;")
where t = extension rate (s-1)
20 V = cone velocity
For a 30 cone moving at 1mm/s, E = 0.249 s-1
Temperature Correction
The hardness (yield stress) of skin cleansing bar formulations is temperature-
sensitive.
For meaningful comparisons, the reading at the target distance (RT) should be
corrected
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to a standard reference temperature (normally 40 C), according to the
following
equation:
R40 = R = x wp: 7-4C/ 1
where R40 = reading at the reference temperature (40 C)
RT = reading at the temperature T
a = coefficient for temperature correction
T = temperature at which the sample was analyzed.
The correction can be applied to the extensional stress.
Raw and Processed Data
The final result is the temperature-corrected force or stress, but it is
advisable to record
the instrument reading and the sample temperature also.
A hardness value of at least 1.2 Kg (measured at 40 C) is acceptable.
Table - 1:
Ingredient (wt%) A 1 B 2 C
3
Sodium 56.8 58.3 57.3 57.3
56.3 56.3
anhydrous soap*
Water 29.0 29.0 30.0 30.0
31.0 31.0
Glycerin 6.0 6.0 6.0 6.0 6.0
6.0
Sodium chloride 1.6 1.6 1.6 1.6 1.6
1.6
Sodium citrate 3.0 3.0 3.0 3.0 3.0
3.0
Aculyn 28 2.0 - 0.5 - 0.5
Polymer as per - 0.5 0.5 -
0.5
the invention
Minor ingredients 1.6 1.6 1.6 1.6 1.6
1.6
(colourants,
perfume,
preservative etc)
Hardness 1.6 2.0 1.4 1.8 1.4
1.6
*The fat blend to prepare the soap was 80% non-lauric and 20% lauric of
vegetable
origin
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The data in the above table indicates that compositions within the invention
(Examples
1 to 3) provide for harder soaps when the polymer of the invention is used
instead of a
well-known commercially available polyacrylate polymer (Aculyn 28) (Examples A
to C)
at the same respective water concentration.
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